Listeria monocytogenes (also known as L. monocytogenes or Listeria) has been recognized as a hazardous organism likely to occur in foodstuffs, such as cooked (ready-to-eat) meat, fish and poultry products. Regarding listeriosis, it is indicated that ready-to-eat-food, such as deli meats and frankfurters both pose a major risk per serving of illness/death from this organism.
A major concern includes the ability of Listeria monocytogenes to survive in processing environments, re-contaminate products during post-thermal processing, and subsequent growth in the finished product at refrigeration temperatures.
It has been indicated that the salts of lactic acid and acetic acid have significant antimicrobial activity against Listeria. Incorporation of lactate and/or diacetate into product formulation has been widely used to prevent growth of Listeria with the advantages of low cost and assurance of residual activity after opening the package (Lianou A., Geornaras I., Kendall P. A., Belk K. E., Scanga J. A., Smith G. C., and Sofos J. N., 2007, Fate of Listeria monocytogenes in commercial ham, formulated with or without antimicrobials under conditions simulating contamination in the processing or retail environment and during home storage, J. Food Prot., 70:378-385).
WO 2011/014669 A1 discloses an antimicrobial preservative composition for food products comprising: lactic acid or a salt thereof, acetic acid or a salt thereof, and propionic acid or a salt thereof. It further discloses a food product and a method for producing the food product comprising the preservative composition.
US patent application 2008/0317921A1 relates as well to the use of salts of lactic acid and/or acetic acid in preservation. It discloses a process for manufacturing a cooked meat product with increased shelf-life stability and an increased resistance against the growth of bacteria. In the process an uncooked meat product is combined with an organic acid salt selected from lactate salts, acetate salts and combinations thereof, and a latent acid, followed by cooking the meat product. The latent acid does not show acidic properties when it is added to the uncooked meat product, but is converted to carboxylic acid during the cooking.
However, since lactates are highly hygroscopic they need to be prepared as a 60% solution (with diacetate). This negatively impacts the flavor (Stekelenburg F. K. and Kant-Muermans M. L. T., 2001, Effects of sodium lactate and other additives in a cooked ham product on sensory quality and development of a strain of Lactobacillus curvatus and Listeria monocytogenes, Int. J. Food Microbiol., 66:197-203).
Further, addition of acids to meat products is associated with a number of disadvantages. The addition of an acidic compound may detrimentally affect the taste of the meat, its structure, and various other properties, such as smell and bite.
This means that a balance needs to be found between the amount and type of acid that can be added without detrimentally affecting the taste of the meat and its other properties, and the microbiological resistance to be obtained.